Submission #209475

#	Time	Username	Problem	Language	Result	Execution time	Memory
209475		my99n	Horses (IOI15_horses)	C++14	17 / 100	175 ms	31596 KiB

horses

#include <bits/stdc++.h>
#include "horses.h"
using namespace std;

const long long mod = 1e9+7;
int n;
long long seg[2000100], x[500100], y[500100], lazy[2000100];

void build (int now = 1, int l = 0, int r = n-1) {
	lazy[now] = 1;
	if (l == r) return void(seg[now] = (x[l]*y[l])%mod);
	int mid = (l+r)/2;
	build(now*2, l, mid); build(now*2+1, mid+1, r);
	seg[now] = max(seg[now*2], seg[now*2+1]);
}

void push (int now) {
	if (lazy[now] == 1) return;
	lazy[now*2] *= lazy[now];
	lazy[now*2] %= mod;
	lazy[now*2+1] *= lazy[now];
	lazy[now*2+1] %= mod;
	seg[now] *= lazy[now];
	seg[now] %= mod;
	lazy[now] = 1;
}

long long query (int now = 1) {
	push(now);
	return seg[now];
}

void update (int a, int b, long long val, int now = 1, int l = 0, int r = n-1) {
	push(now);
	if (r < a or b < l) return;
	if (a <= l and r <= b) {
		lazy[now] *= val;
		lazy[now] %= mod;
		push(now);
		return;
	}
	int mid = (l+r)/2;
	update(a, b, val, now*2, l, mid); update(a, b, val, now*2+1, mid+1, r);
	seg[now] = max(seg[now*2], seg[now*2+1]);
}

long long inverse (long long a, long long n = mod-2) {
	if (n == 1) return a;
	long long r = inverse(a, n/2);
	r *= r;
	r %= mod;
	if (n&1) return (r*a) % mod;
	return r;
}

int init(int N, int X[], int Y[]) {
	n = N;
	x[0] = X[0];							
	for (int i = 1; i < n; i++) {
		x[i] = X[i]*x[i-1];
		x[i] %= mod;
	}
	for (int i = 0; i < n; i++) y[i] = Y[i];
	build(); // for (int i = 0; i < n; i++) cerr << x[i]*y[i] << endl;
	for (int i = 0; i < n; i++) x[i] = X[i];
	return (int)query();
}

int updateX(int pos, int val) {
	update(pos, n-1, inverse(x[pos]));
	x[pos] = val;
	update(pos, n-1, x[pos]);
	return query();
}

int updateY(int pos, int val) {
	update(pos, pos, inverse(y[pos]));
	assert(((inverse(y[pos]) * y[pos]) % mod) == 1);
	y[pos] = val;
	update(pos, pos, y[pos]);
	return query();
}

Compilation message (stderr)

horses.cpp: In function 'long long int inverse(long long int, long long int)':
horses.cpp:47:52: warning: declaration of 'n' shadows a global declaration [-Wshadow]
 long long inverse (long long a, long long n = mod-2) {
                                                    ^
horses.cpp:6:5: note: shadowed declaration is here
 int n;
     ^
horses.cpp: In function 'int updateX(int, int)':
horses.cpp:73:14: warning: conversion to 'int' from 'long long int' may alter its value [-Wconversion]
  return query();
         ~~~~~^~
horses.cpp: In function 'int updateY(int, int)':
horses.cpp:81:14: warning: conversion to 'int' from 'long long int' may alter its value [-Wconversion]
  return query();
         ~~~~~^~

• Subtask 1: 17 / 17
• Subtask 2: 0 / 17
• Subtask 3: 0 / 20
• Subtask 4: 0 / 23
• Subtask 5: 0 / 23